1. Field of the Invention
The present invention relates to a coating apparatus, and more particularly, to a coating apparatus and an operating method thereof that prevent damage to the nozzle of the coating apparatus resulting from impurities on a substrate during resin coating of the substrate, and impurities remaining on a stage at the bottom of the substrate. This especially applies to a spinless coater for coating resin, but may apply to other coaters and other nozzles.
2. Discussion of the Related Art
Recently, the demand for flat panel displays with low profiles, small sizes, low power consumption, and other favorable characteristics, has increased. Of these, liquid crystal display devices (LCDs) with high quality color reproduction are actively being developed.
LCDs have two substrates with electrodes formed on each side thereof, and the sides with the electrodes face one another. Then, a liquid crystal substance is injected between the two substrates. A voltage is supplied to the two electrodes which creates an electromagnetic field that moves the liquid crystal molecules and thus changes the degree of light transmission. An image is thus created.
A lower (array) LCD substrate may include a thin film transistor for applying a pixel electrode signal. This thin film transistor may be formed with a metal layer and an insulating layer through repeated photolithography. The upper substrate of the LCD may include a color filter having colors of red (R), green (G), and blue (B).
FIG. 1 is a schematic view of an LCD structure according to the related art.
Referring to FIG. 1, an LCD according to the related art has a TFT substrate with a TFT array formed thereon, a color filter substrate with a color filter arranged thereon, and liquid crystal filled between the TFT substrate and the color filter substrate, and a back light assembly for supplying light in order to display an image.
The TFT array formed on the TFT substrate relays and controls electrical signals and the liquid crystal controls the amount of light transmitted by altering its molecular arrangement according to an applied voltage. Through this process, controlled light is transmitted through the color filter substrate to display desired colors and images.
When manufacturing the above LCD, the color filter substrate and TFT substrate have a sealing material interposed between them. The sealing material combines the color filter substrate and the TFT substrate, and also acts as a sealant to prevent liquid crystal, injected between the color filter and TFT substrates, from leaking.
Referring to FIGS. 2 and 3, a brief description of the process of coating resin to form the color filter on the color filter substrate will be given. FIG. 2 is a schematic view of the structure of a coating apparatus according to the related art, and FIG. 3 is a perspective view showing a process for coating resin on a color filter substrate performed with a coating apparatus according to the related art.
As shown in FIG. 2, a coating apparatus according to the related art includes a nozzle 207 for discharging resin, and a nozzle support 205 for supporting and moving the nozzle 207. The nozzle support 205 moves along a rail 201, and the nozzle 207 discharges resin onto a substrate 209 (glass, for example) disposed above a stage 203 to form a color filter. Here, the rail 201 may be an air slider rail.
In the coating apparatus according to the related art of FIG. 3, when the nozzle 207 discharges resin onto the substrate 209, tracking sensors 301a and 301b determine whether the nozzle 207 is properly aligned and properly moving over the substrate 209. Here, the tracking sensors 301a and 301b measure a gap between the nozzle 207 and the substrate 209 to determine whether the nozzle 207 deviates from above the substrate 209.
In the process of coating resin on the substrate 209, impurities that resulted from a previous process may be present on the substrate 209. A normal gap between the substrate 209 and the nozzle 207 is about 150 μm, and an impurity such as a particle of glass may be several millimeters. Accordingly, when impurities remain on the substrate 209 during the coating process, the nozzle 207, which is costly, that discharges resin onto the substrate 209 may be damaged.
Furthermore, if an impurity 403 is present on the stage 203 on which the substrate 209 is placed, the problem as illustrated in FIG. 4 occurs. FIG. 4 is a diagram showing a defect that occurs when resin is coated on a substrate 209 while an impurity 403 remains on a stage 203 in a coating apparatus according to the related art. Specifically, when an impurity 403 remains on the stage 203, the impurity 403 is located near the rear surface of the substrate 209, thus producing a defect during the resin coating process.